Spark ignition type engine

Abstract

A spark ignition type engine enabling engine startability to be favorable is provided. The spark ignition type engine includes a main intake-air passage; a throttle valve of the main intake-air passage; a bypass intake-air passage bypassing the throttle valve; an ISC valve of the bypass intake-air passage; and an electronic control device that controls an engine speed by adjusting an opening degree of the ISC valve, in which when the engine is started, cranking is performed at a cranking opening degree at which the ISC valve is narrowed by a predetermined amount from a fully opened state by control of the electronic control device, so that an intake-air negative pressure is generated on an intake-air downstream side of the ISC valve.

What is claimed is: 
     
       1. A spark ignition type engine comprising: a main intake-air passage; a throttle valve of the main intake-air passage; a bypass intake-air passage bypassing the throttle valve; an ISC valve of the bypass intake-air passage; and an electronic control device that controls an engine speed by adjusting an opening degree of the ISC valve,
 wherein when the engine is started, cranking is performed at a cranking opening degree at which the ISC valve is narrowed by a predetermined amount from a fully opened state by control of the electronic control device, so that an intake-air negative pressure is generated on an intake-air downstream side of the ISC valve, 
 the engine comprising: an engine temperature sensor; and an atmospheric pressure sensor, 
 wherein 
 as a detected engine temperature becomes lower, a base lower limit value of an ISC valve opening degree is increased to a fully open side, and 
 the base lower limit value is corrected to increase to the fully open side with an increase correction value based on a detected atmospheric pressure in an engine middle-high temperature range where the engine temperature exceeds a predetermined value, and in the increase correction, the increase correction value is increased to the fully open side as the detected atmospheric pressure becomes lower, and 
 the increase correction is prohibited in an engine low temperature range where the engine temperature is equal to or lower than the predetermined value. 
 
     
     
       2. The spark ignition type engine according to  claim 1  comprising an engine temperature sensor,
 wherein the cranking opening degree of the ISC valve is set to be narrower as a detected engine temperature becomes lower. 
 
     
     
       3. The spark ignition type engine according to  claim 1 , comprising an intake-air temperature sensor,
 wherein the cranking opening degree of the ISC valve is set to be narrower as a detected intake-air temperature is lower. 
 
     
     
       4. The spark ignition type engine according to  claim 2  comprising an intake-air temperature sensor,
 wherein the cranking opening degree of the ISC valve is set to be narrower as a detected intake-air temperature is lower. 
 
     
     
       5. The spark ignition type engine according to  claim 1 , wherein
 the cranking opening degree of the ISC valve is set such that an intake-air amount at a time of cranking is 30% to 70% of a time when the ISC valve is fully opened. 
 
     
     
       6. The spark ignition type engine according to  claim 2 , wherein
 the cranking opening degree of the ISC valve is set such that an intake-air amount at a time of cranking is 30% to 70% of a time when the ISC valve is fully opened. 
 
     
     
       7. The spark ignition type engine according to  claim 3 , wherein
 the cranking opening degree of the ISC valve is set such that an intake-air amount at a time of cranking is 30% to 70% of a time when the ISC valve is fully opened. 
 
     
     
       8. The spark ignition type engine according to  claim 4 , wherein
 the cranking opening degree of the ISC valve is set such that an intake-air amount at a time of cranking is 30% to 70% of a time when the ISC valve is fully opened. 
 
     
     
       9. The spark ignition type engine according to  claim 1 , wherein
 an idling opening degree of the ISC valve immediately after completion of cranking is larger than the cranking opening degree. 
 
     
     
       10. The spark ignition type engine according to  claim 2 , wherein
 an idling opening degree of the ISC valve immediately after completion of cranking is larger than the cranking opening degree. 
 
     
     
       11. The spark ignition type engine according to  claim 3 , wherein
 an idling opening degree of the ISC valve immediately after completion of cranking is larger than the cranking opening degree. 
 
     
     
       12. The spark ignition type engine according to  claim 4 , wherein
 an idling opening degree of the ISC valve immediately after completion of cranking is larger than the cranking opening degree. 
 
     
     
       13. The spark ignition type engine according to  claim 5 , wherein
 an idling opening degree of the ISC valve immediately after completion of cranking is larger than the cranking opening degree. 
 
     
     
       14. The spark ignition type engine according to  claim 1 , wherein
 the increase correction value decreases as the detected engine temperature becomes lower in the engine middle-high temperature range. 
 
     
     
       15. The spark ignition type engine according to  claim 1 , comprising an intake-air temperature sensor,
 wherein the base lower limit value of the ISC valve opening degree is increased to the fully open side as a detected intake-air temperature becomes higher. 
 
     
     
       16. A spark ignition type engine comprising: a main intake-air passage; a throttle valve of the main intake-air passage; a bypass intake-air passage bypassing the throttle valve; an ISC valve of the bypass intake-air passage; and an electronic control device that controls an engine speed by adjusting an opening degree of the ISC valve,
 wherein when the engine is started, cranking is performed at a cranking opening degree at which the ISC valve is narrowed by a predetermined amount from a fully opened state by control of the electronic control device, so that an intake-air negative pressure is generated on an intake-air downstream side of the ISC valve, 
 the engine comprising a sudden acceleration operation detection sensor, 
 wherein 
 when a sudden acceleration operation is not detected under the control of the electronic control device, a normal driving processing is performed, and when the sudden acceleration operation is detected, a sudden acceleration processing is performed over a required duration, and then a transition is made to the normal driving processing, 
 in the sudden acceleration processing, an advance angle of ignition timing is set to be larger than that in the normal driving processing, and is retarded over time during a required duration of the sudden acceleration processing.